Sound amplifying system



XAug; 16, 1932. l w. E. BRINDLEY SOUND AMPLIFYING SYSTEM Filed March 20,1930 l 2 l /7 l W '-5 T /6 1 A INVENTOR V27/mm `E) Bri/147e] ATTORNEYPatented Aug. 16, 1932 lUNITED ASTATES WILLIAM E. BRINDLEY, OFWILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 WESLING- PATENT OFFICE:

HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

SOUND AMPLIFYING SYSTEM Application led March 20, 1930. Serial No.437,378.

My invention pertains to sound amplifying systems and more particularlto a system capable of use as a public a dress system or as anadvertising medium.

In a system as referred to above, an energytranslating device must beused which is capable of reproducing voice and music with a high degreeof amplification. The electrodynamic speaker, of all known types of lduced in two coils, one of which is supplied with a constantunidirectional potential and the other of which is supplied with avariable potential at audio frequency. A speaker of this type, normally,requires two separate sources of energy, one to supply the directcurrent and the other to supply the audio frequency current and twoseparate transmission channels leadingfto the loud speaker coilsheretofore have been considered necessary.

In a public address system or an advertising device where the loudspeaker is located at a distance from the sources of energy, the use ofa dynamic loud speaker proves to be both expensive and inconvenient inthat two transmission channels are required and, in addition, thecapacity between the long leads of the transmission channels providesbypaths for the audio frequency currents, thereby reducing-theefficiency of the system.

One obj ect of my invention is to provide a system of the type referredto above, wherein the energy required by a dynamic loud speaker shall besupplied over a single transmission channel.

Another object of my invention is to provide a system wherein thecurrent from an A. C. source and the current from a D. C. sourcemay'be'superposed on a common'transmission medium and, subsequently,separated to operate a dynamic speaker, thereby eliminating, to a greatextent, the distributcd capacity inherent in prior known systems.

A further object is to provide a system whereby A. C. and D. C. currentsto a dynamic speaker may be supplied from the if space discharge currentof a thermionic device.

An additional object of my invention is to provide a simple andinexpensive system wherein a loud speaker of the dynamic type may beconveniently located at a distanc from its source of energy.

A more specific object is to provide an advertising device wherein acaptive balloon may be, advantageously, utilized to support a loudspeaker of the dynamic type.

Other objects and features of my invention will be disclosed in thefollowing description taken in conjunction with the drawing wherein thefigure represents a specific embodiment of my invention as applied to anadvertising device.

pick-up device 2 which is connected in serieswith a battery 3 and aprimary of a transformer 4f, thereby modulating the current in thatcircuit. This modulated current will be amplified by means of theaudio-frequency amplifier and subsequently impressed on the outputcircuit of the transformer 5.

The output of said transformer is connected to two contacting devices 6and 7 which are adapted to ride upon the edges of two I rotatableconducting spindles 8 and 9, one of said spindles 9 carrying aconducting cable 11 which is adapted to function as an anchor cable of acaptive balloon, the other of said spindles carrying a Windingpreferably of insulated Wire 12 which is in electrical con-V nectionwith said spindle, the free portion of said winding being electricallyconnected to the primary of the transformer 13 and 'to the D. C. coil 14of the loud speaker 15. An insulator 16 serves to maintain the wire andcable in spaced relation. The return paths through said primary and saidD. C. coil terminate in an electrical connection 17 to the anchor cableof the balloon, the output of the transformer serving to supply theenergy necessary to energize the audio-frequency coil of the loudspeaker. The cable and Wire constitute the sole means for conveyingenergy to both the D. C. and A. C. coils of the loud speaker.

A direct-current supply for energizing the D. C. coil of the loudspeaker is disclosed as comprising a full Wave rectifier 18 incombination with an A. C. source of supply, the output of which isconnected to the contactors 6 and 7 thereby impressing the D. C. outputalso upon the transmission channel constituted by the cable 11 and theWire 12. The condenser 19 in the output circuit of the transformer 5 andthe condenser 20 in the input circuit of the transformer 13 function toprevent the direct current from entering the alternatingcurrent circuitsand, in like manner, the choke coils 22 and 23 in the output circuit ofthe rectifying means and the system wherein 'an alternating current anda direct current are superposed upon a common or identical transmissionchannel and, subsequently, separated to supply the direct-current coiland the alternating-current coil of a dynamic speaker with theircorresponding currents.

It will be obvious that a microphone might be used in place of thepick-up mechanism for the purpose of broadcasting speech, and it isWithin the contemplation of my invention to do this.

Although I have disclosed a separate source of direct current toenergize the D. C. coil of the loud speaker, it is within the scope of minvention to utilize the D. C. component ofy the space discharge currentof the audiofrequency amplifier for the same purpose in av mannersuggested in a prior application of mine, Serial No. 251,901.

My invention as described above possesses all the advantages set forthin the objects of my invention', and while I have described theinvention as embodied in an advertising device, it can be used equallyas well for other purposes, such as public address systems, etc.,

and I do not desire to be limited to the speciic disclosure exceptinsofar as the prior art requires it.

I claim as my invention:

1. In a sound amplifying system, means for producing a variable current,means for producing a direct current, an energy translating devicecomprising means responsive to said variable current and meansresponsive to said direct current, asupport for said energytranslatingdevice, and means for conveying said currents to said energy translatingdevice,said conveying means comprising a common transmission channel, atleast one conductor of said transmission channel forming an anchoringcable in said system for said support.

2. In a sound-amplifying system, an energy-translating device of theelectrodynamic type, means for supporting said device, cable means foranchoring said supporting means, a source of alternating current energy,a source of direct current energy, a conductive path from said sourcesto said energy-translating device, said cable anchoring means and saidconductive path comprising the sole means whereby energy may betransmitted from said source to said energy-translating device.

In testimony whereof, I have hereunto subscribed my name this 17th dayof March,

WILLIAB'I E. BRINDLEY.

